Monomeric C-Reactive Protein Generation on Activated Platelets: The Missing Link Between Inflammation and Atherothrombotic Risk

Relative Values of Hematological Indices for Prognosis of Heart Failure: A Mini-Review

Owing to the augmented perception of heart failure (HF) pathophysiology, management of the affected patients has been improved dramatically; as with the identification of the inflammatory background of HF, new avenues of HF prognosis research have been opened up. In this regard, relative values of hematologic indices were demonstrated by a growing body of evidence to successfully predict HF outcomes. Cost-effectiveness, accessibility, and easy obtainability of these relative values make them a precious option for the determination of HF prognosis; particularly in low-income developing countries. In this short review, we aimed to present the current literature on the predictability of these hematologic parameters for HF outcomes.

Functional Foods in Preventing Human Blood Platelet Hyperactivity-Mediated Diseases-An Updated Review

Backgrounds/Objectives: Abnormal platelet functions are associated with human morbidity and mortality. Platelets have emerged as critical regulators of numerous physiological and pathological processes beyond their established roles in hemostasis and thrombosis. Maintaining physiological platelet function is essential to hemostasis and preventing platelet-associated diseases such as cardiovascular disease, cancer metastasis, immune disorders, hypertension, diabetes, sickle cell disease, inflammatory bowel disease, sepsis, rheumatoid arthritis, myeloproliferative disease, and Alzheimer's disease. Platelets become hyperactive in obesity, diabetes, a sedentary lifestyle, hypertension, pollution, and smokers. Platelets, upon activation, can trawl leukocytes and progenitor cells to the vascular sites. Platelets release various proinflammatory, anti-inflammatory, and angiogenic factors and shed microparticles in the circulation, thus promoting pathological reactions. These platelet-released factors also maintain sustained activation, further impacting these disease processes. Although the mechanisms are unknown, multiple stimuli induce platelet hyperreactivity but involve the early pathways of platelet activation. The exact mechanisms of how hyperactive platelets contribute to these diseases are still unclear, and antiplatelet strategies are inevitable for preventing these diseases. Reducing platelet function during the early stages could significantly impact these diseases. However, while this is potentially a worthwhile intervention, using antiplatelet drugs to limit platelet function in apparently healthy individuals without cardiovascular disease is not recommended due to the increased risk of internal bleeding, resistance, and other side effects. The challenge for therapeutic intervention in these diseases is identifying factors that preferentially block specific targets involved in platelets' complex contribution to these diseases while leaving their hemostatic function at least partially intact. Since antiplatelet drugs such as aspirin are not recommended as primary preventives, it is essential to use alternative safe platelet inhibitors without side effects.

METHODS

A systematic search of the PUBMED database from 2000 to 2023 was conducted using the selected keywords: "functional foods", "polyphenols", "fatty acids", "herbs", fruits and vegetables", "cardioprotective agents", "plant", "platelet aggregation", "platelet activation", "clinical and non-clinical trial", "randomized", and "controlled".

RESULTS

Potent natural antiplatelet factors have been described, including omega-3 fatty acids, polyphenols, and other phytochemicals. Antiplatelet bioactive compounds in food that can prevent platelet hyperactivity and thus may prevent several platelet-mediated diseases, including cardiovascular disease.

CONCLUSIONS

This narrative review describes the work during 2000-2023 in developing functional foods from natural sources with antiplatelet effects.

Changes in the Proteome of Platelets from Patients with Critical Progression of COVID-19

Platelets, the smallest cells in human blood, known for their role in primary hemostasis, are also able to interact with pathogens and play a crucial role in the immune response. In severe coronavirus disease 2019 (COVID-19) cases, platelets become overactivated, resulting in the release of granules, exacerbating inflammation and contributing to the cytokine storm. This study aims to further elucidate the role of platelets in COVID-19 progression and to identify predictive biomarkers for disease outcomes. A comparative proteome analysis of highly purified platelets from critically diseased COVID-19 patients with different outcomes (survivors and non-survivors) and age- and sex-matched controls was performed. Platelets from critically diseased COVID-19 patients exhibited significant changes in the levels of proteins associated with protein folding. In addition, a number of proteins with isomerase activity were found to be more highly abundant in patient samples, apparently exerting an influence on platelet activity via the non-genomic properties of the glucocorticoid receptor (GR) and the nuclear factor κ-light-chain-enhancer of activated B cells (NFκB). Moreover, carbonic anhydrase 1 (CA-1) was found to be a candidate biomarker in platelets, showing a significant increase in COVID-19 patients.

Being Eaten Alive: How Energy-Deprived Cells Are Disposed of, Mediated by C-Reactive Protein-Including a Treatment Option

In medicine, C-reactive protein (CRP) has become established primarily as a biomarker, predicting patient prognosis in many indications. Recently, however, there has been mounting evidence that it causes inflammatory injury. As early as 1999, CRP was shown to induce cell death after acute myocardial infarction (AMI) in rats and this was found to be dependent on complement. The pathological effect of CRP was subsequently confirmed in further animal species such as rabbit, mouse and pig. A conceptual gap was recently closed when it was demonstrated that ischemia in AMI or ischemia/hypoxia in the severe course of COVID-19 causes a drastic lack of energy in involved cells, resulting in an apoptotic presentation because these cells cannot repair/flip-flop altered lipids. The deprivation of energy leads to extensive expression on the cell membranes of the CRP ligand lysophosphatidylcholine. Upon attachment of CRP to this ligand, the classical complement pathway is triggered leading to the swift elimination of viable cells with the appearance of an apoptotic cell by phagocytes. They are being eaten alive. This, consequently, results in substantial fibrotic remodeling within the involved tissue. Inhibiting this pathomechanism via CRP-targeting therapy has been shown to be beneficial in different indications.

Predictive value of combining leucocyte and platelet counts for mortality in ST-segment elevation myocardial infarction patients after percutaneous coronary intervention treatment in Chinese population: a retrospective cohort study

OBJECTIVE

Risk stratification is challenging in patients with acute ST segment elevation myocardial infarction (STEMI) after primary percutaneous coronary intervention (PCI). We investigated the prognostic value of a novel score system combining leucocyte and platelet counts (COL-P) scores for in-hospital and long-term adverse outcomes.

DESIGN

This was a retrospective cohort study of patients with STEMI.

SETTING

First Affiliated Hospital of Xinjiang Medical University.

PARTICIPANTS

A total of 854 STEMI patients with primary PCI were included in this study from November 2009 and December 2015.

PRIMARY AND SECONDARY OUTCOME MEASURES

Major adverse cardiovascular events (MACEs).

METHODOLOGY

The patients were divided into three groups according to the COL-P scores (0, 1 and 2). Cox regression analysis was used to investigate the relation between adverse outcomes and the COL-P score in patients with STEMI.

RESULTS

A total of 44 patients died in hospital, and 99 within 3-year follow-up after discharge. The in-hospital and 3-year mortality and MACEs were higher in patients with higher COL-P score. Multivariable Cox regression indicated COL-P score was independently associated with long-term mortality (COL-P 1 vs COL-P 0: HR 2.07, 95% CI 1.016 to 5.567, p=0.005; COL-P 2 vs COL-P 0: HR 5.02, 95% CI 1.990 to 9.041, p<0.001).

CONCLUSION

The COL-P score was a useful risk system for stratifying high-risk patients with STEMI after primary PCI.

A novel phosphocholine-mimetic inhibits a pro-inflammatory conformational change in C-reactive protein

C-reactive protein (CRP) is an early-stage acute phase protein and highly upregulated in response to inflammatory reactions. We recently identified a novel mechanism that leads to a conformational change from the native, functionally relatively inert, pentameric CRP (pCRP) structure to a pentameric CRP intermediate (pCRP*) and ultimately to the monomeric CRP (mCRP) form, both exhibiting highly pro-inflammatory effects. This transition in the inflammatory profile of CRP is mediated by binding of pCRP to activated/damaged cell membranes via exposed phosphocholine lipid head groups. We designed a tool compound as a low molecular weight CRP inhibitor using the structure of phosphocholine as a template. X-ray crystallography revealed specific binding to the phosphocholine binding pockets of pCRP. We provide in vitro and in vivo proof-of-concept data demonstrating that the low molecular weight tool compound inhibits CRP-driven exacerbation of local inflammatory responses, while potentially preserving pathogen-defense functions of CRP. The inhibition of the conformational change generating pro-inflammatory CRP isoforms via phosphocholine-mimicking compounds represents a promising, potentially broadly applicable anti-inflammatory therapy.

C-reactive protein, immunothrombosis and venous thromboembolism

C-reactive protein (CRP) is a member of the highly conserved pentraxin superfamily of proteins and is often used in clinical practice as a marker of infection and inflammation. There is now increasing evidence that CRP is not only a marker of inflammation, but also that destabilized isoforms of CRP possess pro-inflammatory and pro-thrombotic properties. CRP circulates as a functionally inert pentameric form (pCRP), which relaxes its conformation to pCRP* after binding to phosphocholine-enriched membranes and then dissociates to monomeric CRP (mCRP). with the latter two being destabilized isoforms possessing highly pro-inflammatory features. pCRP* and mCRP have significant biological effects in regulating many of the aspects central to pathogenesis of atherothrombosis and venous thromboembolism (VTE), by directly activating platelets and triggering the classical complement pathway. Importantly, it is now well appreciated that VTE is a consequence of thromboinflammation. Accordingly, acute VTE is known to be associated with classical inflammatory responses and elevations of CRP, and indeed VTE risk is elevated in conditions associated with inflammation, such as inflammatory bowel disease, COVID-19 and sepsis. Although the clinical data regarding the utility of CRP as a biomarker in predicting VTE remains modest, and in some cases conflicting, the clinical utility of CRP appears to be improved in subsets of the population such as in predicting VTE recurrence, in cancer-associated thrombosis and in those with COVID-19. Therefore, given the known biological function of CRP in amplifying inflammation and tissue damage, this raises the prospect that CRP may play a role in promoting VTE formation in the context of concurrent inflammation. However, further investigation is required to unravel whether CRP plays a direct role in the pathogenesis of VTE, the utility of which will be in developing novel prophylactic or therapeutic strategies to target thromboinflammation.

Transitional changes in the structure of C-reactive protein create highly pro-inflammatory molecules: Therapeutic implications for cardiovascular diseases

C-reactive protein (CRP) is the prototypic acute-phase reactant that has long been recognized almost exclusively as a marker of inflammation and predictor of cardiovascular risk. However, accumulating evidence indicates that CRP is also a direct pathogenic pro-inflammatory mediator in atherosclerosis and cardiovascular diseases. The 'CRP system' consists of at least two protein conformations with distinct pathophysiological functions. The binding of the native, pentameric CRP (pCRP) to activated cell membranes leads to a conformational change resulting in two highly pro-inflammatory isoforms, pCRP* and monomeric CRP (mCRP). The deposition of these pro-inflammatory isoforms has been shown to aggravate the localized tissue injury in a broad range of pathological conditions including atherosclerosis and thrombosis, myocardial infarction, and stroke. Here, we review recent findings on how these structural changes contribute to the inflammatory response and discuss the transitional changes in the structure of CRP as a novel therapeutic target in cardiovascular diseases and overshooting inflammation.

Pattern Recognition Proteins: First Line of Defense Against Coronaviruses

The rapid outbreak of COVID-19 caused by the novel coronavirus SARS-CoV-2 in Wuhan, China, has become a worldwide pandemic affecting almost 204 million people and causing more than 4.3 million deaths as of August 11 2021. This pandemic has placed a substantial burden on the global healthcare system and the global economy. Availability of novel prophylactic and therapeutic approaches are crucially needed to prevent development of severe disease leading to major complications both acutely and chronically. The success in fighting this virus results from three main achievements: (a) Direct killing of the SARS-CoV-2 virus; (b) Development of a specific vaccine, and (c) Enhancement of the host's immune system. A fundamental necessity to win the battle against the virus involves a better understanding of the host's innate and adaptive immune response to the virus. Although the role of the adaptive immune response is directly involved in the generation of a vaccine, the role of innate immunity on RNA viruses in general, and coronaviruses in particular, is mostly unknown. In this review, we will consider the structure of RNA viruses, mainly coronaviruses, and their capacity to affect the lungs and the cardiovascular system. We will also consider the effects of the pattern recognition protein (PRP) trident composed by (a) Surfactant proteins A and D, mannose-binding lectin (MBL) and complement component 1q (C1q), (b) C-reactive protein, and (c) Innate and adaptive IgM antibodies, upon clearance of viral particles and apoptotic cells in lungs and atherosclerotic lesions. We emphasize on the role of pattern recognition protein immune therapies as a combination treatment to prevent development of severe respiratory syndrome and to reduce pulmonary and cardiovascular complications in patients with SARS-CoV-2 and summarize the need of a combined therapeutic approach that takes into account all aspects of immunity against SARS-CoV-2 virus and COVID-19 disease to allow mankind to beat this pandemic killer.

Serum albumin levels and inflammation

Albumin is the most abundant protein in the plasma and has a regulatory role in the distribution of body fluids, acid-base physiology, and binding of essential components in the bloodstream. C-reactive protein (CRP) is produced by hepatocytes and is commonly used to assess inflammation. It was previously noted that acute-phase concentrations of proteins, such as CRP, tend to rise in inflammatory conditions, while albumin concentrations tend to decline. This study assessed the correlation between albumin levels and various inflammatory indices (CRP, WBC, PLT) of patients hospitalized at the Galilee Medical Center over a period of 3 months. The study population consisted of 4434 patients, ages 18-107 years (mean: 52 years), of whom 60% were female. A negative correlation between albumin and CRP levels (r = -0.311) was identified, as well as between albumin and white blood cells levels (r = -0.157). Positive correlations were found between albumin and platelets levels (r = 0.084), as well as between albumin and hemoglobin levels (r = 0.513). When considering the three largest departments, the strongest negative correlation between albumin and CRP was identified in the Internal Medicine departments. A linear regression analysis discovered a fairly minor effect of CRP on albumin levels, which only became apparent when CRP levels were extremely high (500 mg/L). The mechanisms underlying this negative correlation still need to be explored.

Dietary Antiplatelets: A New Perspective on the Health Benefits of the Water-Soluble Tomato Concentrate Fruitflow®

Our understanding of platelet functionality has undergone a sea change in the last decade. No longer are platelets viewed simply as regulators of haemostasis; they are now acknowledged to be pivotal in coordinating the inflammatory and immune responses. This expanded role for platelets brings new opportunities for controlling a range of health conditions, targeting platelet activation and their interactions with other vascular cells. Antiplatelet drugs may be of wider utility than ever expected but often cause platelet suppression too strong to be used out of clinical settings. Dietary antiplatelets represent a nutritional approach that can be efficacious while safe for general use. In this review, we discuss potential new uses for dietary antiplatelets outside the field of cardiovascular health, with specific reference to the water-soluble tomato extract Fruitflow^®. Its uses in different aspects of inflammation and immune function are discussed, highlighting exercise-induced inflammation, mediating the effects of air pollution, and controlling thrombotic aspects of the immune response. Potential future developments in women’s health, erectile dysfunction, and the allergic response indicate how broad the utility of dietary antiplatelets can be.

Regulation of the Complement System by Pentraxins

The functions of pentraxins, like C-reactive protein (CRP), serum amyloid protein P (SAP) and pentraxin-3 (PTX3), are to coordinate spatially and temporally targeted clearance of injured tissue components, to protect against infections and to regulate related inflammation together with the complement system. For this, pentraxins have a dual relationship with the complement system. Initially, after a focused binding to their targets, e.g., exposed phospholipids or cholesterol in the injured tissue area, or microbial components, the pentraxins activate complement by binding its first component C1q. However, the emerging inflammation needs to be limited to the target area. Therefore, pentraxins inhibit complement at the C3b stage to prevent excessive damage. The complement inhibitory functions of pentraxins are based on their ability to interact with complement inhibitors C4bp or factor H (FH). C4bp binds to SAP, while FH binds to both CRP and PTX3. FH promotes opsonophagocytosis through inactivation of C3b to iC3b, and inhibits AP activity thus preventing formation of the C5a anaphylatoxin and the complement membrane attack complex (MAC). Monitoring CRP levels gives important clinical information about the extent of tissue damage and severity of infections. CRP is a valuable marker for distinguishing bacterial infections from viral infections. Disturbances in the functions and interactions of pentraxins and complement are also involved in a number of human diseases. This review will summarize what is currently known about the FH family proteins and pentraxins that interact with FH. Furthermore, we will discuss diseases, where interactions between these molecules may play a role.

Hydroxycholesterol binds and enhances the anti-viral activities of zebrafish monomeric c-reactive protein isoforms

C-reactive proteins (CRPs) are among the faster acute-phase inflammation-responses proteins encoded by one gene (hcrp) in humans and seven genes (crp1-7) in zebrafish (Danio rerio) with importance in bacterial and viral infections. In this study, we described novel preferential bindings of 25-hydroxycholesterol (25HOCh) to CRP1-7 compared with other lipids and explored the antiviral effects of both 25HOCh and CRP1-7 against spring viremia carp virus (SVCV) infection in zebrafish. Both in silico and in vitro results confirmed the antiviral effect of 25HOCh and CRP1-7 interactions, thereby showing that the crosstalk between them differed among the zebrafish isoforms. The presence of oxidized cholesterols in human atherosclerotic plaques amplifies the importance that similar interactions may occur for vascular and/or neurodegenerative diseases during viral infections. In this context, the zebrafish model offers a genetic tool to further investigate these interactions.

Acetylcholine Inhibits Monomeric C-Reactive Protein Induced Inflammation, Endothelial Cell Adhesion, and Platelet Aggregation; A Potential Therapeutic?

Objectives: In this study, we examined the possibility of using targeted antibodies and the potential of small molecular therapeutics (acetylcholine, nicotine and tacrine) to block the pro-inflammatory and adhesion-related properties of monomeric C-reactive protein (mCRP). Methods: We used three established models (platelet aggregation assay, endothelial leucocyte binding assay and monocyte inflammation via ELISA and Western blotting) to assess the potential of these therapeutics. Results: The results of this study showed that monocyte induced inflammation (raised tumor necrosis factor-alpha-TNF-α) induced by mCRP was significantly blocked in the presence of acetylcholine and nicotine, whilst tacrine and targeted antibodies (clones 8C10 and 3H12) had less of or no significant effects. Western blotting confirmed the ability of acetylcholine to inhibit mCRP-induced cell signaling phosphorylation of extracellular signal regulated kinase 1/2 (ERK1/2), p38 and nuclear factor-kappa B (NF-κB). There was no evidence of direct binding between small molecules and mCRP. mCRP also induced endothelial cell-monocyte adhesion in a dose dependent fashion, however, both acetylcholine and nicotine as well as targeting antibodies notably inhibited adhesion. Finally, we investigated their effects on mCRP-induced platelet aggregation. All three small molecules significantly attenuated platelet aggregation as did the antibody 8C10, although 3H12 had a weaker effect. Discussion: Acetylcholine and to a lesser extent nicotine show potential for therapeutic inhibition of mCRP-induced inflammation and cell and platelet adhesion. These results highlight the potential of targeted antibodies and small molecule therapeutics to inhibit the binding of mCRP by prevention of membrane interaction and subsequent activation of cellular cascade systems, which produce the pro-inflammatory effects associated with mCRP.

C-Reactive Protein (CRP) and Leptin Receptor in Obesity: Binding of Monomeric CRP to Leptin Receptor

While leptin deficiency or dysfunction leads to morbid obesity, obese subjects are characterized paradoxically by hyperleptinemia indicating lack of response to leptin. C-reactive protein (CRP) has been suggested to be a key plasma protein that could bind to leptin. To examine whether CRP interferes with leptin action, mediated through its cell surface receptor, docking studies of CRP with the extracellular domain of the leptin receptor were done employing bioinformatics tools. Monomeric CRP docked with better Z-rank score and more non-bond interactions than pentameric CRP at the CRH2–FNIII domain proximal to the cell membrane, distinct from the leptin-docking site. Interaction of CRP with leptin receptor was validated by solid phase binding assay and co-immunoprecipitation of CRP and soluble leptin receptor (sOb R) from human plasma. Analysis of the serum levels of leptin, CRP, and sOb R by ELISA showed that CRP levels were significantly elevated (p < 0.0001) in non-morbid obese subjects (n = 42) compared to lean subjects (n = 32) and correlated positively with body mass index (BMI) (r = 0.74, p < 0.0001) and leptin (r = 0.8, p < 0.0001); levels of sOb R were significantly low in obese subjects (p < 0.001) and showed a negative correlation with BMI (r = −0.26, p < 0.05) and leptin (r = −0.23, p < 0.05) indicating a minimal role for sOb R in sequestering leptin.

Anti-inflammatory therapies in myocardial infarction: failures, hopes and challenges

In the infarcted heart, the damage-associated molecular pattern proteins released by necrotic cells trigger both myocardial and systemic inflammatory responses. Induction of chemokines and cytokines and up-regulation of endothelial adhesion molecules mediate leukocyte recruitment in the infarcted myocardium. Inflammatory cells clear the infarct of dead cells and matrix debris and activate repair by myofibroblasts and vascular cells, but may also contribute to adverse fibrotic remodelling of viable segments, accentuate cardiomyocyte apoptosis and exert arrhythmogenic actions. Excessive, prolonged and dysregulated inflammation has been implicated in the pathogenesis of complications and may be involved in the development of heart failure following infarction. Studies in animal models of myocardial infarction (MI) have suggested the effectiveness of pharmacological interventions targeting the inflammatory response. This article provides a brief overview of the cell biology of the post-infarction inflammatory response and discusses the use of pharmacological interventions targeting inflammation following infarction. Therapy with broad anti-inflammatory and immunomodulatory agents may also inhibit important repair pathways, thus exerting detrimental actions in patients with MI. Extensive experimental evidence suggests that targeting specific inflammatory signals, such as the complement cascade, chemokines, cytokines, proteases, selectins and leukocyte integrins, may hold promise. However, clinical translation has proved challenging. Targeting IL-1 may benefit patients with exaggerated post-MI inflammatory responses following infarction, not only by attenuating adverse remodelling but also by stabilizing the atherosclerotic plaque and by inhibiting arrhythmia generation. Identification of the therapeutic window for specific interventions and pathophysiological stratification of MI patients using inflammatory biomarkers and imaging strategies are critical for optimal therapeutic design.

Oxidation of C-reactive protein by hypochlorous acid leads to the formation of potent platelet activator

We examined the structural and functional consequences of oxidative modification of C-reactive protein (CRP) by hypochlorous acid (HOCl), which can be generated in vivo via the myeloperoxidase/H₂O₂/Cl^- system. HOCl exposure resulted in the oxidation and chlorination of CRP amino acid residues, leading to protein unfolding, greater surface hydrophobicity and the formation of aggregates. After treatment of isolated platelets with 50μg/ml HOCl-CRP, the modified CRP significantly stimulated platelet activation (over 10-fold increase in the fraction of CD62-positive platelets compared to controls, P<0.008), enhanced deposition of platelets onto immobilized fibrinogen (two-fold rise in platelet adhesion compared to controls, P<0.0001), and induced platelet aggregation by up to 79.5%. The ability of HOCl-CRP to interact with several platelet receptors (TLR-4, GPIIbIIIa) and plasma proteins (C1q, IgG) strongly indicates that HOCl-modification leads to structural changes of CRP resulting in the formation of new ligand binding sites, which is characteristic of the monomeric form of CRP exerting pro-inflammatory effects on a variety of cells. Overall, the oxidation of native CRP by HOCl seems to represent an alternative mechanism of CRP modification, by which CRP reveals its pro-inflammatory and pro-thrombotic properties, and as such, it might be of causal relevance in the pathogenesis of atherosclerosis.

Complement factor H in AMD: Bridging genetic associations and pathobiology

Age-Related Macular Degeneration (AMD) is a complex multifactorial disease characterized in its early stages by lipoprotein accumulations in Bruch's Membrane (BrM), seen on fundoscopic exam as drusen, and in its late forms by neovascularization ("wet") or geographic atrophy of the Retinal Pigmented Epithelial (RPE) cell layer ("dry"). Genetic studies have strongly supported a relationship between the alternative complement cascade, in particular the common H402 variant in Complement Factor H (CFH) and development of AMD. However, the functional significance of the CFH Y402H polymorphism remains elusive. In this article, we critically review the literature surrounding the functional significance of this polymorphism. Furthermore, based on our group's studies we propose a model in which CFH H402 affects CFH binding to heparan sulfate proteoglycans leading to accelerated lipoprotein accumulation in BrM and drusen progression. We also review the literature on the role of other complement components in AMD pathobiologies, including C3a, C5a and the membrane attack complex (MAC), and on transgenic mouse models developed to interrogate in vivo the effects of the CFH Y402H polymorphism.

Neutralization of viral infectivity by zebrafish c-reactive protein isoforms

This work explores the unexpected in vivo and in vitro anti-viral functions of the seven c-reactive protein (crp1-7) genes of zebrafish (Danio rerio). First results showed heterogeneous crp1-7 transcript levels in healthy wild-type zebrafish tissues and organs and how those levels heterogeneously changed not only after bacterial but also after viral infections, including those in adaptive immunity-deficient rag1^-/- mutants. As shown by microarray hybridization and proteomic techniques, crp2/CRP2 and crp5/CRP5 transcripts/proteins were among the most modulated during in vivo viral infection situations including the highest responses in the absence of adaptive immunity. In contrast crp1/CRP1/and crp7/CRP7 very often remained unmodulated. All evidences suggested that zebrafish crp2-6/CRP2-6 may have in vivo anti-viral activities in addition to their well known anti-bacterial and/or physiological functions in mammalians. Confirming those expectations, in vitro neutralization and in vivo protection against spring viremia carp virus (SVCV) infections were demonstrated by crp2-6/CRP2-6 using crp1-7 transfected and/or CRP1-7-enriched supernatant-treated fish cells and crp2-5-injected one-cell stage embryo eggs, respectively. All these findings discovered a crp1-7/CRP1-7 primitive anti-viral functional diversity.These findings may help to study similar functions on the one-gene-coded human CRP, which is widely used as a clinical biomarker for bacterial infections, tissue inflammation and coronary heart diseases.

The combination of CRP isoforms with oxLDL decreases TNF-α and IL-6 release by U937-derived macrophages

C-reactive protein (CRP) and oxidized low density lipoprotein (oxLDL) serve major roles at both early and advanced stages of atherosclerosis. CRP exists in two isoforms, monomeric (m) and pentameric (p), that bring about pro- or anti-inflammatory effects in macrophages. In addition, CRP may form a complex with oxidized low-density lipoprotein (oxLDL) via phosphatidylcholine, thus decreasing its pro-inflammatory effects within macrophages. The aim of the present study was to investigate the single and the combined effects of mCRP, pCRP and oxLDL on U937-derived macrophages. In the current study, U937-derived macrophages were treated in vitro with different combinations of CRP isoforms with or without oxLDL. The levels of major inflammatory cytokines [interleukin (IL)-1β, IL-6, IL-8 and tumor necrosis factor (TNF)-α] along with the production of reactive oxygen species (ROS) were determined. TNF-α and IL-6 levels were significantly decreased (P<0.05) by the effect of mCRP and pCRP combined with oxLDL. No significant changes were observed in IL-1β, IL-8 or ROS levels.

Structure and functionalities of the human c-reactive protein compared to the zebrafish multigene family of c-reactive-like proteins

Because of the recent discovery of multiple c-reactive protein (crp)-like genes in zebrafish (Danio rerio) with predicted heterogeneous phospholipid-binding amino acid sequences and heterogeneous transcript expression levels in viral survivors and adaptive-deficient mutants, zebrafish constitute an attractive new model for exploring the evolution of these protein's functions, including their possible participation in fish trained immunity. Circulating human CRP belongs to the short pentraxin family of oligomeric proteins that are characteristic of early acute-phase innate responses and is widely used as a clinical inflammation marker. In contrast to pentameric human CRP (pCRP), zebrafish CRPs are trimeric (tCRP); however monomeric CRP (mCRP) conformations may also be generated when associated with cellular membranes as occurs in humans. Compared to human CRP, zebrafish CRP-like proteins show homologous amino acid sequence stretches that are consistent with, although not yet demonstrated, cysteine-dependent redox switches, calcium-binding spots, phosphocholine-binding pockets, C1q-binding domains, regions interacting with immunoglobulin Fc receptors (FcR), unique mCRP epitopes, mCRP binding peptides to cholesterol-enriched rafts, protease target sites, and/or binding sites to monocyte, macrophage, neutrophils, platelets and/or endothelial cells. Amino acid variations among the zebrafish CRP-like multiprotein family and derived isoforms in these stretches suggest that functional heterogeneity best fits the wide variety of aquatic pathogens. As occurs in humans, phospholipid-tagged tCRP-like multiproteins might also influence local inflammation and induce innate immune responses; however, in addition, different zebrafish tCRP-like proteins and/or isoforms might fine tune new still unknown functions. The information reviewed here could be of value for future studies not only to comparative but also medical immunologists and/or fisheries sectors. This review also introduces some novel speculations for future studies.

Conformational Changes in C-Reactive Protein Affect Binding to Curved Membranes in a Lipid Bilayer Model of the Apoptotic Cell Surface

C-reactive protein (CRP) is a serum protein that binds to damaged membranes through a phosphatidylcholine binding site. The membrane binding process can initiate the complement immune response and facilitates the clearance of apoptotic cells, likely aiding in the protection of autoimmunity. The initiation of an immune response relies on a conformation change from a native, pentameric form to a modified form, where the modified form binds complement proteins (i.e., C1q) and regulatory proteins substantially better than the native form. In vitro, this reactivity is observed when CRP is monomeric, and a modified form has also been observed at sites of inflammation. Despite evidence that the monomeric form has much higher affinities for almost all proteinaceous binding partners, the role of CRP conformation on lipid binding is yet unknown. In this work, we mimic the outer leaflet of apoptotic cell membranes using a nanopatterned substrate to create curved, supported lipid bilayers and then characterize how CRP conformation affects the interactions between CRP and target membranes. In this assay, the chemical composition and shape are separately tunable parameters. The lipids consisted primarily of palmitoyloleoylphosphatidylcholine, with and without lysophosphatidylcholine, and the curvature had a radius of 27-55 nm. Using this model system combined with quantitative fluorescence microscopy methods, CRP binding to lipid membranes was measured as a function of different conformations of CRP. The modified form of CRP bound curved membranes, but the pentameric form did not for the range of curvatures measured. Unlike most other curvature-sensing proteins, modified CRP accumulated more at a moderate curvature, rather than highly curved or flat regions, suggesting that the membrane bound form does not solely depend on a defect binding mechanism. The presence of lysophosphatidylcholine, a component of apoptotic membranes, increased CRP binding to all types of membranes. Overall, our results show that CRP interactions vary with protein form, lipid composition, and membrane shape. The mechanism by which CRP recognizes damaged membranes depends on the combination of all three.

Purification of recombinant C-reactive protein mutants

C-reactive protein (CRP) is an evolutionarily conserved protein, a component of the innate immune system, and an acute phase protein in humans. In addition to its raised level in blood in inflammatory states, CRP is also localized at sites of inflammation including atherosclerotic lesions, arthritic joints and amyloid plaque deposits. Results of in vivo experiments in animal models of inflammatory diseases indicate that CRP is an anti-pneumococcal, anti-atherosclerotic, anti-arthritic and an anti-amyloidogenic molecule. The mechanisms through which CRP functions in inflammatory diseases are not fully defined; however, the ligand recognition function of CRP in its native and non-native pentameric structural conformations and the complement-activating ability of ligand-complexed CRP have been suggested to play a role. One tool to understand the structure-function relationships of CRP and determine the contributions of the recognition and effector functions of CRP in host defense is to employ site-directed mutagenesis to create mutants for experimentation. For example, CRP mutants incapable of binding to phosphocholine are generated to investigate the importance of the phosphocholine-binding property of CRP in mediating host defense. Recombinant CRP mutants can be expressed in mammalian cells and, if expressed, can be purified from the cell culture media. While the methods to purify wild-type CRP are well established, different purification strategies are needed to purify various mutant forms of CRP if the mutant does not bind to either calcium or phosphocholine. In this article, we report the methods used to purify pentameric recombinant wild-type and mutant CRP expressed in and secreted by mammalian cells.

Systemic inflammatory profiles and their relationships with demographic, behavioural and clinical features in acute low back pain

Systemic inflammation is linked with development and persistence of many pathological pain states. Although chronic phase inflammatory responses are well reported, the acute phase has received limited attention. Here we investigated circulating pro-inflammatory cytokines and C-reactive protein (CRP), and explored their relationships with symptom severity and other factors in acute low back pain (LBP). Ninety-nine individuals within two weeks of onset of acute LBP and 55 pain-free controls completed questionnaires related to their pain (visual analogue scale, VAS) and disability, behaviour, sleep quality and psychological status. CRP, interleukin-6 (IL-6), tumor necrosis factor (TNF) and interleukin-1β (IL-1β) were measured from serum samples. Biomarkers were compared between LBP and control participants, and in a separate analysis, for those with "high-pain" (VAS ⩾4) and "low-pain" (VAS <4). The relationships between biomarkers and all other variables, including other cytokines/CRP were assessed. CRP was higher in LBP than controls and in those with high- than low-pain (p<0.01). IL-6 was higher in those with high- than low-pain (p<0.05), but not controls. Various pain and non-pain factors were associated with each biomarker differently. These findings suggest systemic CRP and IL-6 are important contributors to inflammation in the early post-onset phase of LBP and that various factors can shape these responses.

Targeting C-Reactive Protein in Inflammatory Disease by Preventing Conformational Changes

C-reactive protein (CRP) is a pentraxin that has long been employed as a marker of inflammation in clinical practice. Recent findings brought up the idea of CRP to be not only a systemic marker but also a mediator of inflammation. New studies focused on structural changes of the plasma protein, revealing the existence of two distinct protein conformations associated with opposed inflammatory properties. Native, pentameric CRP (pCRP) is considered to be the circulating precursor form of monomeric CRP (mCRP) that has been identified to be strongly proinflammatory. Recently, a dissociation mechanism of pCRP has been identified on activated platelets and activated/apoptotic cells associated with the amplification of the proinflammatory potential. Correspondingly, CRP deposits found in inflamed tissues have been identified to exhibit the monomeric conformation by using conformation-specific antibodies. Here we review the current literature on the causal role of the dissociation mechanism of pCRP and the genesis of mCRP for the amplification of the proinflammatory potential in inflammatory reactions such as atherosclerosis and ischemia/reperfusion injury. The chance to prevent the formation of proinflammatory mediators in ubiquitous inflammatory cascades has pushed therapeutic strategies by targeting pCRP dissociation in inflammation. In this respect, the development of clinically applicable derivatives of the palindromic compound 1,6-bis(phosphocholine)-hexane (1,6-bis PC) should be a major focus of future CRP research.

Impact of platelet phenotype on myocardial infarction

In acute myocardial infarction patients the injured vascular wall triggers thrombus formation in the damage site. Fibrin fibers and blood cellular elements are the major components of thrombus formed in acute occlusion of coronary arteries. It has been established that the initial thrombus is primarily composed of activated platelets rapidly stabilized by fibrin fibers. This review highlights the role of platelet membrane phenotype in pathophysiology of myocardial infarction. Here, we regard platelet phenotype as quantitative and qualitative parameters of the plasma membrane outer surface, which are crucial for platelet participation in blood coagulation, development of local inflammation and tissue repair.

C-Reactive Protein: An In-Depth Look into Structure, Function, and Regulation

Cardiovascular disease is the leading cause of morbidity and mortality in the adult population worldwide, with atherosclerosis being its key pathophysiologic component. Atherosclerosis possesses a fundamental chronic inflammatory aspect, and the involvement of numerous inflammatory molecules has been studied in this scenario, particularly C-reactive protein (CRP). CRP is a plasma protein with strong phylogenetic conservation and high resistance to proteolysis, predominantly synthesized in the liver in response to proinflammatory cytokines, especially IL-6, IL-1β, and TNF. CRP may intervene in atherosclerosis by directly activating the complement system and inducing apoptosis, vascular cell activation, monocyte recruitment, lipid accumulation, and thrombosis, among other actions. Moreover, CRP can dissociate in peripheral tissue—including atheromatous plaques—from its native pentameric form into a monomeric form, which may also be synthesized de novo in extrahepatic sites. Each form exhibits distinct affinities for ligands and receptors, and exerts different effects in the progression of atherosclerosis. In view of epidemiologic evidence associating high CRP levels with cardiovascular risk—reflecting the biologic impact it bears on atherosclerosis—measurement of serum levels of high-sensitivity CRP has been proposed as a tool for assessment of cardiovascular risk.

Mutations of C-reactive protein (CRP) -286 SNP, APC and p53 in colorectal cancer: implication for a CRP-Wnt crosstalk

C-reactive protein (CRP) is an established marker of inflammation with pattern-recognition receptor-like activities. Despite the close association of the serum level of CRP with the risk and prognosis of several types of cancer, it remains elusive whether CRP contributes directly to tumorigenesis or just represents a bystander marker. We have recently identified recurrent mutations at the SNP position -286 (rs3091244) in the promoter of CRP gene in several tumor types, instead suggesting that locally produced CRP is a potential driver of tumorigenesis. However, it is unknown whether the -286 site is the sole SNP position of CRP gene targeted for mutation and whether there is any association between CRP SNP mutations and other frequently mutated genes in tumors. Herein, we have examined the genotypes of three common CRP non-coding SNPs (rs7553007, rs1205, rs3093077) in tumor/normal sample pairs of 5 cancer types (n = 141). No recurrent somatic mutations are found at these SNP positions, indicating that the -286 SNP mutations are preferentially selected during the development of cancer. Further analysis reveals that the -286 SNP mutations of CRP tend to co-occur with mutated APC particularly in rectal cancer (p = 0.04; n = 67). By contrast, mutations of CRP and p53 or K-ras appear to be unrelated. There results thus underscore the functional importance of the -286 mutation of CRP in tumorigenesis and imply an interaction between CRP and Wnt signaling pathway.

A conformational change of C-reactive protein in burn wounds unmasks its proinflammatory properties

Tissue damage in burn injury leads to a rapid increase of leukocytes and acute phase reactants. Plasma levels of C-reactive protein (CRP) rise within hours after the insult. No deficiency of this protein has been reported in humans, suggesting it plays a pivotal role in innate immunity. CRP in circulation is composed of five identical subunits [pentameric CRP (pCRP)]. Recently, deposits of structurally modified CRP (mCRP) have been found in inflammatory diseases. Little is known about this structural change and how it affects CRP functions. We analyzed CRP deposits in burn wounds and serum by immunohistochemistry, western blot and dot blot analysis. CRP was deposited in necrotic and inflamed tissue, but not in adjacent healthy tissue. Tissue deposited CRP was detected by mCRP-specific antibodies and structurally different from serum pCRP. mCRP but not pCRP induced reactive oxygen species production by monocytes and facilitated uptake of necrotic Jurkat cells by macrophages. In addition, it accelerated migration of keratinocytes in a scratch wound assay. The structural changes that occur in pCRP upon localization to damaged and inflamed tissue in burn wounds result in a functionally altered protein with distinct functions. mCRP exhibits opsonic, proinflammatory and promigratory properties which modulate wound healing.

C-reactive protein and lung diseases

C-reactive protein (CRP), a member of the pentraxin family of plasma proteins, is one of the most distinctive acute phase reactants. In response to inflammation, cell damage or tissue injury, plasma level of CRP rapidly and dramatically increases up to 1000-fold, a phenomenon that has been used for years to monitor infections and many destructive/inflammatory conditions. The magnitude of CRP increase usually correlates with the severity of injury or inflammation and reflects an important physiological role of this interesting but still under-investigated protein. It is now generally accepted that CRP is involved in host defense and inflammation. However, the exact function of this protein in health and disease remains unclear. Many studies have demonstrated that in different pathophysiological conditions CRP might be involved in the regulation of lung function and may participate in the pathogenesis of various pulmonary disorders. The fluctuation of CRP concentrations in both alveolar fluid and serum associated with different pulmonary diseases suggests its important role in lung biology. Discussion of the still controversial functions of CRP in lung physiology and diseases is the main focus of this review.

The binding of monomeric C-reactive protein (mCRP) to Integrins αvβ3 and α4β1 is related to its pro-inflammatory action

The prototypic acute phase reactant C-reactive protein (CRP) is not only a marker but also a potential contributor to inflammatory diseases. CRP exists as the circulating native, pentameric CRP (pCRP) and the monomeric isoform (mCRP), formed as a result of a dissociation process of pCRP. mCRP is highly pro-inflammatory, but pCRP is not. The mechanism of pro-inflammatory action of mCRP is unclear. We studied the role of integrins in pro-inflammatory action of mCRP. Docking simulation of interaction between mCRP and integrin αvβ3 predicted that mCRP binds to αvβ3 well. We found that mCRP actually bound to integrins αvβ3 and α4β1 well. Antagonists to αvβ3 or α4β1 effectively suppressed the interaction, suggesting that the interaction is specific. Using an integrin β1 mutant (β1-3-1) that has a small fragment from the ligand binding site of β3, we showed that mCRP bound to the classical RGD-binding site in αvβ3. We studied the role of integrins in CRP signaling in monocytic U937 cells. Integrins αvβ3 and α4β1 specifically mediated binding of mCRP to U937 cells. mCRP induced AKT phosphorylation, but not ERK1/2 phosphorylation, in U937 cells. Notably, mCRP induced robust chemotaxis in U937 cells, and antagonists to integrins αvβ3 and α4β1 and an inhibitor to phosphatidylinositide 3-kinase, but not an MEK inhibitor, effectively suppressed mCRP-induced chemotaxis in U937 cells. These results suggest that the integrin and AKT/phosphatidylinositide 3-kinase pathways play a role in pro-inflammatory action of mCRP in U937 cells. In contrast, pCRP is predicted to have a limited access to αvβ3 due to steric hindrance in the simulation. Consistent with the prediction, pCRP was much less effective in integrin binding, chemotaxis, or AKT phosphorylation. These findings suggest that the ability of CRP isoforms to bind to the integrins is related to their pro-inflammatory action.

Post-translational control of protein function by disulfide bond cleavage

Protein action in nature is largely controlled by the level of expression and by post-translational modifications. Post-translational modifications result in a proteome that is at least two orders of magnitude more diverse than the genome. There are three basic types of post-translational modifications: covalent modification of an amino acid side chain, hydrolytic cleavage or isomerization of a peptide bond, and reductive cleavage of a disulfide bond. This review addresses the modification of disulfide bonds. Protein disulfide bonds perform either a structural or a functional role, and there are two types of functional disulfide: the catalytic and allosteric bonds. The allosteric disulfide bonds control the function of the mature protein in which they reside by triggering a change when they are cleaved. The change can be in ligand binding, substrate hydrolysis, proteolysis, or oligomer formation. The allosteric disulfides are cleaved by oxidoreductases or by thiol/disulfide exchange, and the configurations of the disulfides and the secondary structures that they link share some recurring features. How these bonds are being identified using bioinformatics and experimental screens and what the future holds for this field of research are also discussed.

Inflammatory serum proteome pattern in mice fed a high-fat diet

To investigate the influence of diet on serum protein pattern, mice were fed for 8 weeks either control chow or a high-fat diet (containing 21 % w/w milk fat and 0.2 % w/w cholesterol); sera were collected and analyzed by 2-DE. The main positive acute-phase reactant proteins, haptoglobin and hemopexin, were significantly up-regulated in animals receiving the high-fat diet. Data on all other proteins also pointed to an inflammatory condition in these animals. The largest change in concentration was observed for carboxylesterase N, a circulating enzyme seldom connected with lipid metabolism in earlier reports. These observations agree with the notion of a link between diet-induced hyperlipidemia and the inflammatory component of its cardiovascular sequels in humans, but the effects in the experimental animals are massive and obviously affect most of the major serum proteins.

An eicosanoid-centric view of atherothrombotic risk factors

Cardiovascular disease is the foremost cause of morbidity and mortality in the Western world. Atherosclerosis followed by thrombosis (atherothrombosis) is the pathological process underlying most myocardial, cerebral, and peripheral vascular events. Atherothrombosis is a complex and heterogeneous inflammatory process that involves interactions between many cell types (including vascular smooth muscle cells, endothelial cells, macrophages, and platelets) and processes (including migration, proliferation, and activation). Despite a wealth of knowledge from many recent studies using knockout mouse and human genetic studies (GWAS and candidate approach) identifying genes and proteins directly involved in these processes, traditional cardiovascular risk factors (hyperlipidemia, hypertension, smoking, diabetes mellitus, sex, and age) remain the most useful predictor of disease. Eicosanoids (20 carbon polyunsaturated fatty acid derivatives of arachidonic acid and other essential fatty acids) are emerging as important regulators of cardiovascular disease processes. Drugs indirectly modulating these signals, including COX-1/COX-2 inhibitors, have proven to play major roles in the atherothrombotic process. However, the complexity of their roles and regulation by opposing eicosanoid signaling, have contributed to the lack of therapies directed at the eicosanoid receptors themselves. This is likely to change, as our understanding of the structure, signaling, and function of the eicosanoid receptors improves. Indeed, a major advance is emerging from the characterization of dysfunctional naturally occurring mutations of the eicosanoid receptors. In light of the proven and continuing importance of risk factors, we have elected to focus on the relationship between eicosanoids and cardiovascular risk factors.

Expression, crystallization and preliminary crystallographic analysis of C-reactive protein from zebrafish

C-reactive protein (CRP) is an acute phase protein that is found in blood, the concentration of which in plasma rises rapidly in response to inflammation. It functions as a pattern-recognition molecule, recognizing dead cells and various pathogenic agents and eliminating them by utilizing the classical complement pathway and activating macrophages. CRP is phylogenetically highly conserved in invertebrates and mammals. To date, information on the CRP gene has been reported from numerous species of animals, but little is known about the structure of CRP from species other than humans. In order to solve the structure of CRP from bony fish, the CRP gene from zebrafiah (Danio rerio) was cloned and expressed in Escherichia coli. The zebrafish CRP (Dare-CRP) was then purified and crystallized. The crystal diffracted to 2.3 Å resolution and belonged to space group R3, with unit-cell parameters a = b = 114.7, c = 61.0 Å. The Matthews coefficient and solvent content were calculated to be 3.28 Å(3) Da(-1) and 62.55%, respectively. Determination of the zebrafish CRP structure should be helpful in investigating the evolution of CRPs in the innate immune system.

Amyloid plaques dissociate pentameric to monomeric C-reactive protein: a novel pathomechanism driving cortical inflammation in Alzheimer's disease?

Beta-amyloid (Aβ) plaques and local inflammation are central to the pathogenesis of Alzheimer's disease. Although an association between circulating pentameric C-reactive protein (pCRP) and Alzheimer's disease has been reported no pathomechanistic link has been established. We hypothesized that Aβ plaques induce the dissociation of pCRP to individual monomers (mCRP), which possess strong pro-inflammatory properties not shared with pCRP and localizing inflammation to Alzheimer's plaques. pCRP was incubated with Aβ plaques generated in vitro and with non-aggregated Aβ(42) peptide. pCRP dissociation to mCRP was found only when co-incubated with Aβ plaques. Furthermore, sections of frontal cortex from brains of patients with and without Alzheimer's disease were stained with antibodies specific for mCRP and pCRP. There was significantly more mCRP in the cortex of Alzheimer's disease patients (P ≤ 0.01). In contrast, there was no significant difference in pCRP staining. These findings establish that Aβ plaques possess a previously unrecognized potential to dissociate pentameric CRP to monomeric CRP. The existence of mCRP but not pCRP in the brains of Alzheimer's disease patients strongly indicates that this newly described biological effect of Aβ plaques is relevant in Alzheimer pathobiology; potentially localizing and amplifying inflammation via the strong pro-inflammatory effects of locally generated mCRP.

Platelet dysfunction in vascular pathologies and how can it be treated

Cardiovascular diseases are one of the leading causes of morbidity and mortality in industrialized countries, and although many processes play a role in the development of vascular disease, thrombosis is the primary event that precipitates stroke and acute coronary syndromes. The blood platelets are of significant importance in medicine. These cells are involved in many physiological processes, particularly haemostasis through their ability to aggregate and form clots in response to activation. In addition, these dynamic cells display activities that extend beyond thrombosis, including an important role in initiating and sustaining vascular inflammation. The expansion of knowledge from basic and clinical research has highlighted the critical position of platelets in several inflammatory diseases such as arthritis and atherosclerosis. Platelets are emerging as important mediators of inflammation and provide important signals to mediate phenotype of other blood and vascular cells. The important role of platelets in arterial thrombosis and the onset of acute myocardial infarction after atherosclerotic plaque rupture make inhibition of platelet aggregation a critical step in preventing thrombotic events associated with stroke, heart attack, and peripheral arterial thrombosis. However, the use of platelet inhibitors for thrombosis prevention must seek a delicate balance between inhibiting platelet activation and an associated increased bleeding risk. The aim of this review is to up-date the knowledge on platelets physiology and dysfunction in pathologies, such as diabetes mellitus, hypercholesterolemia, and hypertension, emphasizing the link between platelets and the inflammation-related atherosclerosis. The review evaluates the opportunities offered by the novel platelet inhibitors to efficiently alleviate the thrombotic events.

Opposing effects of monomeric and pentameric C-reactive protein on endothelial progenitor cells

C-reactive protein (CRP) has been linked to the pathogenesis of atherosclerosis. The dissociation of native, pentameric (p)CRP to monomeric (m)CRP on the cell membrane of activated platelets has recently been demonstrated. The dissociation of pCRP to mCRP may explain local pro-inflammatory reactions at the site of developing atherosclerotic plaques. As a biomarker, pCRP predicts cardiovascular adverse events and so do reduced levels and function of circulating endothelial progenitor cells (EPCs). We hypothesised that mCRP and pCRP exert a differential effect on EPC function and differentiation. EPCs were treated with mCRP or pCRP for 72 h, respectively. Phenotypical characterisation was done by flow cytometry and immunofluorescence microscopy, while the effect of mCRP and pCRP on gene expression was examined by whole-genome gene expression analysis. The functional capacity of EPCs was determined by colony forming unit (CFU) assay and endothelial tube formation assay. Double staining for acetylated LDL and ulex lectin significantly decreased in cells treated with pCRP. The length of tubuli in a matrigel assay with HUVECs decreased significantly in response to pCRP, but not to mCRP. The number of CFUs increased after pCRP treatment. RNA expression profiling demonstrated that mCRP and pCRP cause highly contradictory gene regulation. Interferon-responsive genes (IFI44L, IFI44, IFI27, IFI 6, MX1, OAS2) were among the highly up-regulated genes after mCRP, but not after pCRP treatment. In conclusion, EPC phenotype, genotype and function were differentially affected by mCRP and pCRP, strongly arguing for differential roles of these two CRP conformations. The up-regulation of interferon-inducible genes in response to mCRP may constitute a mechanism for the local regulation of EPC function.

A proteomic analysis of C-reactive protein stimulated THP-1 monocytes

Background

C-reactive protein (CRP) is a predictor of cardiovascular risk. It circulates as a pentameric protein in plasma. Recently, a potential dissociation mechanism from the disc-shaped pentameric CRP (pCRP) into single monomers (monomeric or mCRP) has been described. It has been shown that mCRP has strong pro-inflammatory effects on monocytes. To further define the role of mCRP in determining monocyte phenotype, the effects of CRP isoforms on THP-1 protein expression profiles were determined. The hypothesis to be tested was that mCRP induces specific changes in the protein expression profile of THP-1 cells that differ from that of pCRP.

Methods

Protein cell lysates from control and mCRP, pCRP or LPS-treated THP-1 cells were displayed using 2-dimensional SDS PAGE and compared. Differentially expressed proteins were identified by MALDI-TOF MS and confirmed by Western blotting.

Results

mCRP significantly up-regulates ubiquitin-activating enzyme E1, a member of the ubiquitin-proteasome system in THP-1 monocytes. Furthermore, HSP 70, alpha-actinin-4 (ACTN4) and alpha-enolase/enolase 1 were upregulated. The proteomic profile of LPS and pCRP treated monocytes differ significantly from that of mCRP.

Conclusion

The data obtained in this study support the hypothesis that isoform-specific effects of CRP may differentially regulate the phenotype of monocytes.

Platelets: pleiotropic roles in atherogenesis and atherothrombosis

Platelets are small, anucleate blood elements of critical importance in cardiovascular disease. The ability of platelets to activate and aggregate to form blood clots in response to endothelial injury, such as plaque rupture, is well established. These cells are therefore important contributors to ischaemia in atherothrombosis, and antiplatelet therapy is effective for this reason. However, growing evidence suggests that platelets are also important mediators of inflammation and play a central role in atherogenesis itself. Interactions between activated platelets, leukocytes and endothelial cells trigger autocrine and paracrine activation signals, resulting in leukocyte recruitment at and into the vascular wall. Direct physical interaction may contribute also, through platelet adhesion molecules assisting localization of monocytes to the site of atherogenesis and platelet granule release contributing to the chronic inflammatory milieu which leads to foam cell development and accelerated atherogenesis. Recent studies have shown that antiplatelet therapy in animal models of accelerated atherogenesis can lead to decreased plaque size and improve plaque stability. This review examines the complexity of platelet function and the nature of interactions between activated platelets, leukocytes and endothelial cells. We focus on the growing body of evidence that platelets play a critical role in atherogenesis and contribute to progression of atherosclerosis.